dm: split discard requests on target boundaries

Update __clone_and_map_discard to loop across all targets in a DM
device's table when it processes a discard bio.  If a discard crosses a
target boundary it must be split accordingly.

Update __issue_target_requests and __issue_target_request to allow a
cloned discard bio to have a custom start sector and size.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 561313a7dac23b76ce5a4cce1ced33dc067be5d5..ac384b2a6a3396238e9f0810cbeee52d08cd7fa7 100644 (file)
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1193,7 +1193,7 @@ static struct dm_target_io *alloc_tio(struct clone_info *ci,
 }
 
 static void __issue_target_request(struct clone_info *ci, struct dm_target *ti,
-                                  unsigned request_nr)
+                                  unsigned request_nr, sector_t len)
 {
        struct dm_target_io *tio = alloc_tio(ci, ti);
        struct bio *clone;
@@ -1208,17 +1208,21 @@ static void __issue_target_request(struct clone_info *ci, struct dm_target *ti,
        clone = bio_alloc_bioset(GFP_NOIO, ci->bio->bi_max_vecs, ci->md->bs);
        __bio_clone(clone, ci->bio);
        clone->bi_destructor = dm_bio_destructor;
+       if (len) {
+               clone->bi_sector = ci->sector;
+               clone->bi_size = to_bytes(len);
+       }
 
        __map_bio(ti, clone, tio);
 }
 
 static void __issue_target_requests(struct clone_info *ci, struct dm_target *ti,
-                                   unsigned num_requests)
+                                   unsigned num_requests, sector_t len)
 {
        unsigned request_nr;
 
        for (request_nr = 0; request_nr < num_requests; request_nr++)
-               __issue_target_request(ci, ti, request_nr);
+               __issue_target_request(ci, ti, request_nr, len);
 }
 
 static int __clone_and_map_empty_barrier(struct clone_info *ci)
@@ -1227,7 +1231,7 @@ static int __clone_and_map_empty_barrier(struct clone_info *ci)
        struct dm_target *ti;
 
        while ((ti = dm_table_get_target(ci->map, target_nr++)))
-               __issue_target_requests(ci, ti, ti->num_flush_requests);
+               __issue_target_requests(ci, ti, ti->num_flush_requests, 0);
 
        ci->sector_count = 0;
 
@@ -1253,32 +1257,27 @@ static void __clone_and_map_simple(struct clone_info *ci, struct dm_target *ti)
 static int __clone_and_map_discard(struct clone_info *ci)
 {
        struct dm_target *ti;
-       sector_t max;
+       sector_t len;
 
-       ti = dm_table_find_target(ci->map, ci->sector);
-       if (!dm_target_is_valid(ti))
-               return -EIO;
-
-       /*
-        * Even though the device advertised discard support,
-        * reconfiguration might have changed that since the
-        * check was performed.
-        */
+       do {
+               ti = dm_table_find_target(ci->map, ci->sector);
+               if (!dm_target_is_valid(ti))
+                       return -EIO;
 
-       if (!ti->num_discard_requests)
-               return -EOPNOTSUPP;
-
-       max = max_io_len(ci->sector, ti);
-
-       if (ci->sector_count > max)
                /*
-                * FIXME: Handle a discard that spans two or more targets.
+                * Even though the device advertised discard support,
+                * reconfiguration might have changed that since the
+                * check was performed.
                 */
-               return -EOPNOTSUPP;
+               if (!ti->num_discard_requests)
+                       return -EOPNOTSUPP;
 
-       __issue_target_requests(ci, ti, ti->num_discard_requests);
+               len = min(ci->sector_count, max_io_len_target_boundary(ci->sector, ti));
 
-       ci->sector_count = 0;
+               __issue_target_requests(ci, ti, ti->num_discard_requests, len);
+
+               ci->sector += len;
+       } while (ci->sector_count -= len);
 
        return 0;
 }